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Group AB is associated with an increased risk of severe E. coli infection.

Some strains of Escherichia coli have surface antigens analogous to the human blood group ABH antigens, and that these are carbohydrates associated with membrane lipopolysaccharides. This study has demonstrated that E. coli strains Y1089 and Y1090 possess the H antigen of blood type O, which can also be converted to the A antigen, again illustrating how by converting one blood type antigen into another gut bacteria can produce opposing blood type 'immunization' and cause digestive intolerance. (1)

The really dangerous variant of E .coli bacteria (called ˘O157:H7÷) was first recognized as a cause of human disease in 1982. Large outbreaks of E. coli O157:H7 have been reported in the United States, including an outbreak in 1993 linked to undercooked hamburgers that resulted in more than 600 reported cases and 4 deaths. In 1996, more than 6000 schoolchildren in Japan developed E. coli O157:H7 infection from eating contaminated radish sprouts. Though vegan enthusiasts tend to emphasize meat as a cause of E. coli infection, since 1995 rew sprouts have been associated with 13 outbreaks of food borne disease due to E. coli or Salmonella. Contamination of the sprouts themselves rather than improper handling, is believed to be the source of the problem.

In most cases the infection is limited to diarrhea and cramps, although in advanced cases the diarrhea can be bloody and debilitating. In fewer than 2% to 7% of those infected, particularly in the very young and the very old, a disorder called Hemolytic uremic syndrome (HUS) will develop. A bacterial toxin damages small blood vessels in the kidney, reduces platelet counts, and destroys red blood cells. Kidney function can be greatly reduced to the degree that dialysis may be necessary. There are no currently available treatments that can prevent HUS once a person is infected with the organism.

It appears that many of the variants of E. coli have developed individualized tastes for different ABO blood types. Even their 'strategies' differ from blood type to blood type:

Attachment -Type A: Many of the bad forms of E. coli express rope-like bundles of filaments, termed bundle-forming pili (BFP). Which allow them to attach to the lining of the intestines. These 'bad' E. coli have suction-cup like lectins on their pili that attach to the various sugars (glycoproteins or glycolipids) comprising the polysaccharides of the intestinal mucus lining. Many of these sugars are in fact, particular ABO antigens. For example, certain E. coli strains which colonize the human digestive tract express lectins specific for different glycolipids called a 'globoseries.' One such glycolipid, globo-A, is restricted to individuals of blood group A with a positive secretor state. (2)

Mimickry- Types B and AB: It appears that many forms of E. coli capable of causing diarrhea are immunologically 'B-like'. That is, they possess an antigen on their surface which resembles the antigen which conveys 'type B blood.' Several studies show a higher number of type B and AB people (who cannot manufacture anti-B antibodies) being afflicted with E. coli caused gastroenteritis. In one study, 148 Egyptian patients were studied for parasitic and bacterial infections in relation to ABO blood groups. There was a 'significant relationship' between blood group B and an excess among cases of E. coli (46.15%). The expected frequency of type B should have been around 11%. (3)

It has been hypothesized for years that the reason certain individuals manufacture antibodies to opposing blood types is a result of 'inapparent immunization' by bacteria antigens in the gut. The hypothesis that naturally occurring anti-B (in those individuals who are type O or type A blood) protects against type B like E . coli infection was verified in a second study (4) which looked at the blood groups of 115 patients with E. coli infection and compared these with three "control" populations: 138 patients with infection due to other organisms; 23,135 hospitalized patients; and 40,038 normal blood donors. The incidence of B and AB blood types , (who cannot make anti-B antibodies) in the E. coli infection group was significantly higher than A and O blood types (who can make anti-B antibodies).

Interaction- Type O: There is an association of type O blood with the severity of the diarrhea that results from E. coli infection. During studies of diarrhea due to Escherichia coli in 316 adult volunteers, ABO and Rh blood group determinations were done to look for differences in the severity of illness in association with certain blood groups. Volunteers with O blood group had a significantly higher attack rate for diarrhea than persons with other blood groups. (5). The authors in this case speculated that there was an interaction between the type O blood group substance and the toxin produced by the bacteria.

Though certainly no substitute for avoidance, infection with E. coli might at least result in one positive outcome: People recovering from E. coli enteritis apparently have higher levels of anti-Thomsen Friedenreich (TF) antibodies. The TF antigen is often expressed in cancer cells, so perhaps an E. coli infection might protect against certain cancers.